Orientation of a nematic liquid crystal near a polymer layer determined by Fourier transform infrared spectroscopy

Abstract

The comprehension of the mechanism of alignment of a liquid crystal by a rubbed polymer layer is a current interest from a fundamental point of view but also in regards to applications. To understand the mechanism of alignment it is necessary to clarify how the liquid crystal is oriented near a surface. A nematic liquid crystal (LC) has a longer a uniaxial symmetry near a rubbed polymer surface but exhibits a biaxial orientation. We probed the thickness dependence of the orientation of a LC using Fourier Transform Infrared Spectroscopy. By this method it can be shown that the order parameter is lower near the surface than in the bulk and that the symmetry of a nematic liquid crystal close to the surface of the alignment layer is not longer uniaxial.